If you are skeptical, and you should be, you might assume these SIRT mutant mice could just be sick and, therefore, short lived. But adding in more copies of the sirtuin genes SIRT1 and SIRT6 does just the opposite: it increases the health and extends the lifespan of mice, just as adding extra copies of the yeast SIR2 gene does in yeast.29 Credit for these discoveries goes to two of my previous colleagues, Shin-ichiro Imai, my former drinking buddy at the Guarente lab, and Haim Cohen, my first postdoc at Harvard. In yeast, we had shown that DNA breaks cause sirtuins to relocalize away from
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